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The apical meristem of Arabidopsis thaliana adventitious roots in planta and in vitro: quiescent center organization and auxin role
No full textQuiescent center organization and auxin role in the root apical meristem of Arabidopsis thaliana adventitious roots in planta and in vitro
No full textAdventitious rooting is a process essential for the survival of numerous plant species because provides anchorage and contributes to water-use efficiency and extraction of nutrients from the soil. In Arabidopsis seedlings adventitious root (AR) formation is increased by exogenous auxin, darkness and specific sucrose concentrations [Takahashi et al, J Plant Res (2003); Falasca and Altamura, Plant Biosystems (2003)]. Stem thin cell layers (TCLs) produce ARs in vitro under darkness combined with of auxin (IBA/NAA) and, mainly, with auxin (IBA) and cytokinin (Kin) [Falasca et al, Plant Cell Rep (2004)]. Indeterminate growth in the primary root (PR), and the organization of all the tissues of the primary body of PR, lateral, and adventitious roots is determined by the stem niche cells, i.e. the initial cells and the quiescent center (QC) cells in the apical meristem. However, the organization and activity of the stem cell niche in the ARs still needs investigation. To this aim, we investigated the organization of stem cell niche and the possible role of auxin in its maintenance in the ARs, in planta and in TCLs. We selected QC marker lines previously used for PR and lateral roots (LRs) (i.e., QC25, pAGL42:GFP, and pWOX5:GFP), [Sabatini et al, Cell (1999); Nawy et al, Plant Cell (2005); Ding and Friml, PNAS (2010)]. Moreover, a DR5:GUS line (harbouring the uidA gene driven by the auxin-inducible DR5 promoter) and a PIN1:GUS line were used to monitor auxin localization in the apical meristem. The seedlings were grown under darkness either without hormones (HF) or with NAA, Kin, IBA, and IBA plus Kin, and the developmental stages of ARs were characterized. The definition of the QC, and the localization of the auxin maximum, were also investigated in the ARs from TCLs cultured with IBA plus Kin. AR formation in planta was enhanced by NAA, IBA and IBA plus Kin, in comparison with the HF condition, whereas it was sporadic with Kin alone. However, NAA treatment induced anomalies in comparison with IBA+Kin treatment. DR5:GUS and PIN1:GUS activities were observed in the dividing cells involved in AR formation, independently on the hormonal treatment. During AR development, a gradient of DR5 activity was established, and it was similar to the pattern of DR5 activity previously observed during LR formation [Benková et al, Cell (2003)]. In planta the QC was defined in the AR primordia at the same stage in which its definition occurs in the LR primordia [Malamy and Benfey, Development (1997)]. Anomalous expression of the QC markers, DR5:GUS and PIN1:GUS constructs occurred in the anomalous ARs formed in the NAA treatment. In vitro, the ARs produced by the TCLs showed DR5:GUS activity at the apex, and the expression of the QC markers was the same as in ARs in planta, sustaining the important role of auxin and cytokinin in the stem cell niche formation and activity in the ARs of Arabidopsis
Development of the quiescent center and definition of the auxin maximum in Arabidopsis adventitious roots in planta and in thin cell layers
No full textIn Arabidopsis adventitious roots (ARs) are induced by darkness [Takahashi et al, J Plant Res (2003)]. Stem thin cell layers (TCLs)
produce ARs in vitro under darkness and with auxin (IBA or NAA) and, mainly, auxin (IBA) plus cytokinin (Kin) [Falasca et al, Plant Cell Rep (2004)]. We investigated the definition of the quiescent center (QC) and the auxin maximum in the ARs in planta and in TCLs. We used QC marker lines previously used in lateral roots (LR) (i.e., QC25 and pAGL42:GFP) and a DR5:GUS line (harbouring uidA gene driven by the auxin-inducible DR5 promoter). The seedlings were grown under darkness either without hormones (HF) or with NAA, Kin, and IBA plus Kin. The definition of the QC and the auxin maximum were also investigated in the ARs from TCLs cultured with IBA plus Kin. AR formation in planta was enhanced by NAA and IBA plus Kin in comparison with the HF medium, and was sporadic with Kin alone. At day 11 after sowing ARs at various stages were similarly present in NAA- and IBA+Kin-grown seedlings, but AR anomalies increased with NAA. DR5:GUS activity was observed in the dividing hypocotyl cells involved in AR formation independently on the hormonal treatment. During AR
development, a gradient of DR5 activity was established, and it was similar to the pattern of DR5 activity during lateral rooting [Benkova et al, Cell (2003)].The QC was defined in the AR primordia in planta at the same stage in which it occurs in LR primordia [Malamy and Benfey Development (1997)], and the expression of the QC markers and DR5:GUS construct was concomitant. Anomalous expression of the QC markers and DR5:GUS construct occurred in the anomalous ARs of the NAA treatment. The ARs produced by the TCLs showed DR5:GUS activity at the tip, and QC markers expression as in ARs in planta. In conclusion, QC definition and auxin maximum are related
events in the ARs in planta and in vitro
Definition of the quiescent center in the root meristem of Arabidopsis adventitious roots
No full textEffects of methyl jasmonate on adventitious rooting from in vitro cultured tobacco thin cell layers
No full textEffetti dell'interazione fra metil giasmonato ed auxina nella rizogenesi avventizia in Nicotiana tabacum
No full textOrganizzazione del centro quiscente e dell’attività del meristema apicale nelle radici avventizie di Arabidopsis thaliana (L.) Heynh.
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
EIN2 and COI1 control the antagonism between ethylene and jasmonate in adventitious rooting of Arabidopsis thaliana thin cell layers
Full text linkAuxins induce adventitious roots (ARs) in numerous culture-systems, and indole-3-butyric acid (IBA) is frequently the best AR-inducer. Vitamin requirements vary according to species, explant, and culture-conditions. Arabidopsis thaliana thin cell layers (AtTCLs) are uncapable of AR-formation on hormone-free medium containing thiamine and myo-inositol, whereas ARs are induced when IBA (10 μM), with/without kinetin (Kin, 0.1 μM), is added. The research frst aim was to determine whether a synergism between IBA and myo-inositol and thiamine was necessary for AR-formation. Results showed that IBA induced AR-formation without myo-inositol and thiamine, but better when both vitamins were also present. Deciphering hormonal action on AR formation under optimal vitamin content would be essential for improving the AR process. Ethylene (ET)/jasmonic acid (JA) signaling cross-talk has been demonstrated as being involved in AR-formation in IBA+Kincultured AtTCLs, by using ein3eil1 and coi1-16 mutants. ETHYLENE INSENSITIVE3 (EIN3)/EIN3-LIKE1 (EIL1) are positive regulators of ethylene (ET)-signaling, whereas CORONATINE INSENSITIVE1 (COI1) is involved in JA-signaling. The ETHYLENE INSENSITIVE2 (EIN2) protein activates EIN3/EIL1 in ET-presence. To understand whether EIN2 was also involved, the AR-response of ein2-1 and coi1-16 TCLs was evaluated adding the ET-precursor 1-aminocyclopropane1-carboxylic acid (ACC, 0.1 μM) and/or the JA-donor methyl jasmonate (JAMe, 0.01 μM) to IBA+vitamins-containing medium. AR-formation was enhanced by JAMe, reduced by ACC, but unchanged by JAMe+ACC in the wild type TCLs, whereas remained similarly low in ein2-1 and coi1-16 under all treatments. Collectively, these results demonstrate that the antagonism between JA and ET in AR-formation from AtTCLs involves a cross-talk by EIN2 and COI1
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